Make the diagnostic message more readable

compiler/rustc_typeck/src/check/upvar.rs

@@ -511,8 +511,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         };
 
                     let diagnostic_msg = format!(
-                        "`{}` causes {} to be fully captured",
-                        migration_string, migrated_variables_concat
+                        "add a dummy let to cause {} to be fully captured",
+                        migrated_variables_concat
                     );
 
                     diagnostics_builder.span_suggestion(

src/test/ui/closures/2229_closure_analysis/migrations/insignificant_drop.fixed

@@ -14,7 +14,7 @@ fn test1_all_need_migration() {
 
     let c = || { let _ = (&t, &t1, &t2); 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP:` let _ = (&t, &t1, &t2)` causes `t`, `t1`, `t2` to be fully captured
+    //~| HELP: add a dummy let to cause `t`, `t1`, `t2` to be fully captured
 
         let _t = t.0;
         let _t1 = t1.0;
@@ -33,7 +33,7 @@ fn test2_only_precise_paths_need_migration() {
 
     let c = || { let _ = (&t, &t1); 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP:` let _ = (&t, &t1)` causes `t`, `t1` to be fully captured
+    //~| HELP: add a dummy let to cause `t`, `t1` to be fully captured
         let _t = t.0;
         let _t1 = t1.0;
         let _t2 = t2;
@@ -49,7 +49,7 @@ fn test3_only_by_value_need_migration() {
     let t1 = (String::new(), String::new());
     let c = || { let _ = &t; 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
         println!("{}", t1.1);
     };
@@ -67,7 +67,7 @@ fn test4_only_non_copy_types_need_migration() {
 
     let c = || { let _ = &t; 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
         let _t1 = t1.0;
     };
@@ -85,7 +85,7 @@ fn test5_only_drop_types_need_migration() {
 
     let c = || { let _ = &t; 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
         let _s = s.0;
     };
@@ -100,7 +100,7 @@ fn test6_move_closures_non_copy_types_might_need_migration() {
     let t1 = (String::new(), String::new());
     let c = move || { let _ = (&t1, &t); 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = (&t1, &t)` causes `t1`, `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t1`, `t` to be fully captured
         println!("{} {}", t1.1, t.1);
     };
 
@@ -115,7 +115,7 @@ fn test7_drop_non_drop_aggregate_need_migration() {
 
     let c = || { let _ = &t; 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
     };
 

src/test/ui/closures/2229_closure_analysis/migrations/insignificant_drop.rs

@@ -14,7 +14,7 @@ fn test1_all_need_migration() {
 
     let c = || {
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP:` let _ = (&t, &t1, &t2)` causes `t`, `t1`, `t2` to be fully captured
+    //~| HELP: add a dummy let to cause `t`, `t1`, `t2` to be fully captured
 
         let _t = t.0;
         let _t1 = t1.0;
@@ -33,7 +33,7 @@ fn test2_only_precise_paths_need_migration() {
 
     let c = || {
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP:` let _ = (&t, &t1)` causes `t`, `t1` to be fully captured
+    //~| HELP: add a dummy let to cause `t`, `t1` to be fully captured
         let _t = t.0;
         let _t1 = t1.0;
         let _t2 = t2;
@@ -49,7 +49,7 @@ fn test3_only_by_value_need_migration() {
     let t1 = (String::new(), String::new());
     let c = || {
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
         println!("{}", t1.1);
     };
@@ -67,7 +67,7 @@ fn test4_only_non_copy_types_need_migration() {
 
     let c = || {
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
         let _t1 = t1.0;
     };
@@ -85,7 +85,7 @@ fn test5_only_drop_types_need_migration() {
 
     let c = || {
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
         let _s = s.0;
     };
@@ -100,7 +100,7 @@ fn test6_move_closures_non_copy_types_might_need_migration() {
     let t1 = (String::new(), String::new());
     let c = move || {
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = (&t1, &t)` causes `t1`, `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t1`, `t` to be fully captured
         println!("{} {}", t1.1, t.1);
     };
 
@@ -115,7 +115,7 @@ fn test7_drop_non_drop_aggregate_need_migration() {
 
     let c = || {
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
     };
 

src/test/ui/closures/2229_closure_analysis/migrations/insignificant_drop.stderr

@@ -16,7 +16,7 @@ note: the lint level is defined here
    |
 LL | #![deny(disjoint_capture_drop_reorder)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-help: `let _ = (&t, &t1, &t2)` causes `t`, `t1`, `t2` to be fully captured
+help: add a dummy let to cause `t`, `t1`, `t2` to be fully captured
    |
 LL |     let c = || { let _ = (&t, &t1, &t2); 
 LL |
@@ -39,7 +39,7 @@ LL | |         let _t2 = t2;
 LL | |     };
    | |_____^
    |
-help: `let _ = (&t, &t1)` causes `t`, `t1` to be fully captured
+help: add a dummy let to cause `t`, `t1` to be fully captured
    |
 LL |     let c = || { let _ = (&t, &t1); 
 LL |
@@ -61,7 +61,7 @@ LL | |         println!("{}", t1.1);
 LL | |     };
    | |_____^
    |
-help: `let _ = &t` causes `t` to be fully captured
+help: add a dummy let to cause `t` to be fully captured
    |
 LL |     let c = || { let _ = &t; 
 LL |
@@ -83,7 +83,7 @@ LL | |         let _t1 = t1.0;
 LL | |     };
    | |_____^
    |
-help: `let _ = &t` causes `t` to be fully captured
+help: add a dummy let to cause `t` to be fully captured
    |
 LL |     let c = || { let _ = &t; 
 LL |
@@ -105,7 +105,7 @@ LL | |         let _s = s.0;
 LL | |     };
    | |_____^
    |
-help: `let _ = &t` causes `t` to be fully captured
+help: add a dummy let to cause `t` to be fully captured
    |
 LL |     let c = || { let _ = &t; 
 LL |
@@ -126,7 +126,7 @@ LL | |         println!("{} {}", t1.1, t.1);
 LL | |     };
    | |_____^
    |
-help: `let _ = (&t1, &t)` causes `t1`, `t` to be fully captured
+help: add a dummy let to cause `t1`, `t` to be fully captured
    |
 LL |     let c = move || { let _ = (&t1, &t); 
 LL |
@@ -146,7 +146,7 @@ LL | |         let _t = t.0;
 LL | |     };
    | |_____^
    |
-help: `let _ = &t` causes `t` to be fully captured
+help: add a dummy let to cause `t` to be fully captured
    |
 LL |     let c = || { let _ = &t; 
 LL |

src/test/ui/closures/2229_closure_analysis/migrations/migrations_rustfix.fixed

@@ -18,7 +18,7 @@ fn closure_contains_block() {
     let t = (Foo(0), Foo(0));
     let c = || { let _ = &t; 
         //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-        //~| HELP: `let _ = &t` causes `t` to be fully captured
+        //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
     };
 
@@ -29,7 +29,7 @@ fn closure_doesnt_contain_block() {
     let t = (Foo(0), Foo(0));
     let c = || { let _ = &t; t.0 };
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
 
     c();
 }

src/test/ui/closures/2229_closure_analysis/migrations/migrations_rustfix.rs

@@ -18,7 +18,7 @@ fn closure_contains_block() {
     let t = (Foo(0), Foo(0));
     let c = || {
         //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-        //~| HELP: `let _ = &t` causes `t` to be fully captured
+        //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
     };
 
@@ -29,7 +29,7 @@ fn closure_doesnt_contain_block() {
     let t = (Foo(0), Foo(0));
     let c = || t.0;
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
 
     c();
 }

src/test/ui/closures/2229_closure_analysis/migrations/migrations_rustfix.stderr

@@ -14,7 +14,7 @@ note: the lint level is defined here
    |
 LL | #![deny(disjoint_capture_drop_reorder)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-help: `let _ = &t` causes `t` to be fully captured
+help: add a dummy let to cause `t` to be fully captured
    |
 LL |     let c = || { let _ = &t; 
 LL |
@@ -29,7 +29,7 @@ error: drop order affected for closure because of `capture_disjoint_fields`
 LL |     let c = || t.0;
    |             ^^^^^^
    |
-help: `let _ = &t` causes `t` to be fully captured
+help: add a dummy let to cause `t` to be fully captured
    |
 LL |     let c = || { let _ = &t; t.0 };
    |                ^^^^^^^^^^^^^^^^^^^

src/test/ui/closures/2229_closure_analysis/migrations/precise.fixed

@@ -18,7 +18,7 @@ fn test_precise_analysis_drop_paths_not_captured_by_move() {
 
     let c = || { let _ = &t; 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
         let _t = &t.1;
     };
@@ -41,7 +41,7 @@ fn test_precise_analysis_long_path_missing() {
 
     let c = || { let _ = &u; 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &u` causes `u` to be fully captured
+    //~| HELP: add a dummy let to cause `u` to be fully captured
         let _x = u.0.0;
         let _x = u.0.1;
         let _x = u.1.0;

src/test/ui/closures/2229_closure_analysis/migrations/precise.rs

@@ -18,7 +18,7 @@ fn test_precise_analysis_drop_paths_not_captured_by_move() {
 
     let c = || {
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
         let _t = &t.1;
     };
@@ -41,7 +41,7 @@ fn test_precise_analysis_long_path_missing() {
 
     let c = || {
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &u` causes `u` to be fully captured
+    //~| HELP: add a dummy let to cause `u` to be fully captured
         let _x = u.0.0;
         let _x = u.0.1;
         let _x = u.1.0;

src/test/ui/closures/2229_closure_analysis/migrations/precise.stderr

@@ -15,7 +15,7 @@ note: the lint level is defined here
    |
 LL | #![deny(disjoint_capture_drop_reorder)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-help: `let _ = &t` causes `t` to be fully captured
+help: add a dummy let to cause `t` to be fully captured
    |
 LL |     let c = || { let _ = &t; 
 LL |
@@ -38,7 +38,7 @@ LL | |         let _x = u.1.0;
 LL | |     };
    | |_____^
    |
-help: `let _ = &u` causes `u` to be fully captured
+help: add a dummy let to cause `u` to be fully captured
    |
 LL |     let c = || { let _ = &u; 
 LL |

src/test/ui/closures/2229_closure_analysis/migrations/significant_drop.fixed

@@ -24,7 +24,7 @@ fn test1_all_need_migration() {
 
     let c = || { let _ = (&t, &t1, &t2); 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP:` let _ = (&t, &t1, &t2)` causes `t`, `t1`, `t2` to be fully captured
+    //~| HELP: add a dummy let to cause `t`, `t1`, `t2` to be fully captured
         let _t = t.0;
         let _t1 = t1.0;
         let _t2 = t2.0;
@@ -42,7 +42,7 @@ fn test2_only_precise_paths_need_migration() {
 
     let c = || { let _ = (&t, &t1); 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP:` let _ = (&t, &t1)` causes `t`, `t1` to be fully captured
+    //~| HELP: add a dummy let to cause `t`, `t1` to be fully captured
         let _t = t.0;
         let _t1 = t1.0;
         let _t2 = t2;
@@ -58,7 +58,7 @@ fn test3_only_by_value_need_migration() {
     let t1 = (Foo(0), Foo(0));
     let c = || { let _ = &t; 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
         println!("{:?}", t1.1);
     };
@@ -75,7 +75,7 @@ fn test4_type_contains_drop_need_migration() {
 
     let c = || { let _ = &t; 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
     };
 
@@ -90,7 +90,7 @@ fn test5_drop_non_drop_aggregate_need_migration() {
 
     let c = || { let _ = &t; 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
     };
 
@@ -103,7 +103,7 @@ fn test6_significant_insignificant_drop_aggregate_need_migration() {
 
     let c = || { let _ = &t; 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = &t` causes `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.1;
     };
 
@@ -118,7 +118,7 @@ fn test7_move_closures_non_copy_types_might_need_migration() {
 
     let c = move || { let _ = (&t1, &t); 
     //~^ ERROR: drop order affected for closure because of `capture_disjoint_fields`
-    //~| HELP: `let _ = (&t1, &t)` causes `t1`, `t` to be fully captured
+    //~| HELP: add a dummy let to cause `t1`, `t` to be fully captured
         println!("{:?} {:?}", t1.1, t.1);
     };